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| A tube fulgurite and a more irregular specimen. |
Fulgurites (from the Latin fulgur meaning thunderbolt) are a variety of the questionable[further explanation needed] mineral lechatelierite. They are natural hollow glass tubes formed in quartzose sand, silica, or soil by lightning strikes.[1] They are formed when lightning with a temperature of at least 1,800 °C (3,270 °F) instantaneously melts silica on a conductive surface and fuses grains together; the fulgurite tube is the cooled product.[2] This process occurs over a period of around one second,[3] and leaves evidence of the lightning path and its dispersion over the surface.[4] They are sometimes referred to as petrified lightning.
Fulgurites can also be produced when a high voltage electrical distribution network breaks and the lines fall onto a conductive surface with sand beneath. The glass formed is called lechatelierite which may also be formed by meteorite impact and volcanic explosions. Because it is amorphous, fulgurite is classified as a mineraloid. Fulgurites can have deep penetrations, sometimes occurring as far as 15 metres (49 ft) below the surface that was struck.[5]
The tubes can be up to several centimeters in diameter, and meters long. The longest fulgurite to have been found is a little over 4.9 m (16 ft) in length, and was found in northern Florida, USA.[3] Their color varies depending on the composition of the sand they formed in, ranging from black or tan to green or a translucent white. The interior is normally very smooth or lined with fine bubbles; the exterior is generally coated with rough sand particles and is porous. They are rootlike in appearance and often show branching or small holes. Fulgurites occasionally form as glazing on solid rocks (sometimes referred to as an exogenic fulgurite).[6]
Fulgurites are appreciated by many for their scientific value.[7] The fact that fulgurites are so abundant in the Saharan Desert shows that lightning was once a frequent occurrence in that region.[8]
Fulgurites are also popular among hobbyists.[9]
[edit] References
- ^ Codding, Penelope W. (1998). Structure-based drug design. Springer. p. 27. ISBN 0-7923-5202-5.
- ^ Carl Ege. "What are fulgurites and where can they be found?". geology.utah.gov. Retrieved 2009-03-21.
- ^ a b Grapes, R. H. (2006). Pyrometamorphism. Springer. p. 28. ISBN 3-540-29453-8.
- ^ Uman, Martin A. (2008). The Art and Science of Lightning Protection. Cambridge University Press. p. 212. ISBN 0-521-87811-X.
- ^ Ripley, George; Charles Anderson Dana (1859). The New American Cyclopaedia. Appleton. p. 2.
- ^ Exogenic fulgurites from Elko County, Nevada: a new class of fulgurite associated with large soil-gravel fulgurite tubes (Rocks & Minerals, Sep/Oct 2004, Vol. 79, No. 5.)
- ^ Chambers's journal By William Chambers, Robert Chambers
- ^ Vladimir A. Rakov, Lightning Makes Glass, 29th Annual Conference of the Glass Art Society, 1999, University of Florida, Gainesville
- ^ Patti Polk, Collecting Rocks, Gems & Minerals: Easy Identification - Values - Lapidary Uses, Krause, 2010, page 168 ISBN 978-1-4402-0415-9
[edit] External links
- Fulgurites in New Scientist (subscription required)
- Glossary of Meteorology definitions (including Fulgurite).
- Petrified Lightning by Peter E. Viemeister (pdf)
- Mindat with location data
- W. M. Myers and Albert B. Peck, A Fulgurite from South Amboy, New Jersey, American Mineralogist, Volume 10, pages 152-155, 1925
- Vladimir A. Rakov, Lightning Makes Glass, 29th Annual Conference of the Glass Art Society, Tampa, Florida, 1999
- Interview (The Event: Petrified Lightning from Central Florida) with artist Allan McCollum along with an historical archive of sixty-six downloadable PDF's on the subject of fulgurites.
- Yale Bulletin and Calendar Yale's Peabody Museum of Natural History displays the longest known preserved fulgurite.
- [1] Binding
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